This invention relates to an adsorption process for drying a gaseous stream and in particular, wherein the gaseous stream is fed, during an adsorption phase, to the inlet of an adsorber and, after passing through an adsorption bed, the dried gaseous stream is withdrawn from the outlet end of the adsorber, and wherein, after termination of the adsorption phase, a purge gas introduced via the outlet end of the adsorber is passed through the adsorber at an elevated temperature, and purge gas loaded with desorbed steam is withdrawn from the inlet end of the adsorber.
A process of this type is described in DAS 2,064,137. However, difficulties arise in utilizing such a process for the drying of a gas containing polymer-forming components. Such components include, for example, unsaturated hydrocarbons or aldehydes found, for example, in synthesis gases or in cracked gases. These components are normally adsorbed during an adsorption phase, but not entirely desorbed during regeneration at elevated temperature since a portion thereof is converted under the regenerating conditions into polymers. The thus-formed polymers coat the surface of the adsorbent thereby resulting in a decrease in the adsorption capacity of the adsorber.
In order to avoid this undesirable effect, an adsorbent can be employed which prevents adsorption of polymer-forming components. Especially suitable for this purpose are zeolitic molecular sieves of the 3A type. However, the use of such adsorbents is frequently impossible, since they are very sensitive mechanically and can readily disintegrate into dust and fragments.
Both of the conventional procedures are less than desirable inasmuch as the adsorbent must be replaced after a relatively short period of time.